Systems and Methods for Inertial Sensing for VAD Diagnostics and Closed Loop Control

ABSTRACT

A blood circulation assist system includes a ventricular assist device (VAD) and a controller. The VAD is attachable to a heart of a patient to pump blood from a ventricle of the heart into a blood vessel of the patient. The VAD includes an impeller, a motor stator operable to rotate the impeller, and an accelerometer generating an accelerometer output indicative of accelerations of the VAD. The controller controls operation of the motor stator to control rotational speed of the impeller based on the accelerometer output.

CROSS REFERENCE TO RELATED APPLICATION DATA

The present application is a Continuation of U.S. patent applicationSer. No. 16/511,641 filed Jul. 15, 2019 (Allowed); which claims thebenefit of U.S. Provisional Appln No. 62/699,500 filed Jul. 17, 2018;the full disclosures which are incorporated herein by reference in theirentirety for all purposes.

BACKGROUND

Ventricular assist devices, known as VADs, are used for both short-term(i.e., days, months) and long-term blood circulation assistance (i.e.,years or a lifetime) where a patient's heart is incapable of providingadequate circulation, commonly referred to as heart failure orcongestive heart failure. According to the American Heart Association,more than five million Americans are living with heart failure, withabout 670,000 new cases diagnosed every year. People with heart failureoften have shortness of breath and fatigue. Years of living with blockedarteries and/or high blood pressure can leave a heart too weak to pumpenough blood to the body. As symptoms worsen, advanced heart failuredevelops.

A patient suffering from heart failure may use a VAD while awaiting aheart transplant or as a long term destination therapy. A patient mayalso use a VAD while recovering from heart surgery. Thus, a VAD cansupplement a weak heart (i.e., partial support) or can effectivelyreplace the natural heart's function.

BRIEF SUMMARY

The following presents a simplified summary of some embodiments of theinvention in order to provide a basic understanding of the invention.This summary is not an extensive overview of the invention. It is notintended to identify key/critical elements of the invention or todelineate the scope of the invention. Its sole purpose is to presentsome embodiments of the invention in a simplified form as a prelude tothe more detailed description that is presented later.

Blood circulation assist systems and related methods employ aventricular assist device (VAD) that includes an accelerometer tomeasure accelerations of the VAD for use in controlling operation of theVAD, generating patient monitoring data, and/or generating VADmonitoring data. In some embodiments, the measured accelerations areprocessed to measure patient activity level, which is used to controlthe output level of the VAD based on the patient activity level. In suchembodiments, the output level of the VAD can be increased in response toan increase in the patient activity level and decreased in response to adecrease in the patient activity level. In some embodiments, themeasured accelerations are processed to track the patient's cardiaccycle timing, which is used to control variation in output of the VAD insynchronization with the patient's cardiac cycle timing. In someembodiments, the measured accelerations are used to generate patientmonitoring data and/or VAD monitoring data. By controlling operation ofthe VAD based on patient activity level and/or in synch with thepatient's cardiac cycle timing, the circulatory support provided isbetter tailored to the needs of the patient, and may thereby producebetter results. Additionally, the availability of the patient monitoringdata and/or the VAD tracking data may enable increased ability todiagnose patient health issues and/or VAD operational problems.

Thus, in one aspect, a blood circulation assist system includes aventricular assist device (VAD) and a controller. The VAD is coupleableto a heart of a patient to pump blood from a ventricle of the heart intoa blood vessel of the patient. The VAD includes an impeller, a motorstator operable to rotate the impeller, and an accelerometer generatingan accelerometer output indicative of accelerations of the VAD. Thecontroller controls operation of the motor stator to control rotationalspeed of the impeller based on the accelerometer output.

In some embodiments, the controller controls variation in output of theVAD in synch with the cardiac cycle timing of the heart. For example, insome embodiments the controller processes the accelerometer output todetect cardiac cycle timing of the heart. The cardiac cycle timing caninclude a heart rate of the patient and a time of occurrence for each ofone or more cardiac cycle events for the heart. The controller can varythe rotational speed of the impeller in sync with the cardiac cycletiming. In some embodiments, the controller varies the rotational speedto increase a rate at which the VAD pumps blood from the ventricle tothe blood vessel during ventricular systole.

In some embodiments, the controller detects the cardiac cycle timing bymeasuring heart wall motion. For example, the controller can process theaccelerometer output to measure motion of a heart wall of the heart towhich the VAD is attached. The controller can detect timing ofventricular systole of the heart based on the motion of the heart wall.

In some embodiments, the controller detects the cardiac cycle timingbased on at least one heart sound. For example, the controller canprocess the accelerometer output to detect a time of occurrence of atleast one heart sound. The controller can detect timing of ventricularsystole of the heart based on the time of occurrence of the at least oneheart sound. In some embodiments, the at least one heart sound includesa sound of closure of the atrioventricular valves of the heart, and/or asound of closure of the semilunar valves of the heart.

In some embodiments, the controller detects the cardiac cycle timing bydetecting variation in drive current supplied to the VAD. For example,in some embodiments the controller: (a) controls the motor stator torotate the impeller at a constant speed throughout at least one completecardiac cycle of the heart, (b) monitors drive current supplied to themotor stator to rotate the impeller at the constant speed, and (c)processes the monitored drive current to detect the cardiac cycle timingof the heart. In some embodiments, the controller varies the rotationalspeed of the impeller during ventricular systole of the heart toincrease a rate at which the VAD pumps blood from the ventricle to theblood vessel.

In some embodiments, the controller synchronizes the output of the VADwith a target cardiac cycle based on detected timing of one or moreprevious cardiac cycles. For example, in some embodiments the controllervaries the rotational speed of the impeller over a target cardiac cycleof the heart based on detected timing of one or more cardiac cycles ofthe heart that occur prior to the target cardiac cycle.

In some embodiments, the controller synchronizes the output of the VADwith a target cardiac cycle based on detected timing of the targetcardiac cycle. For example, in some embodiments, the controller variesthe rotational speed of the impeller over a target cardiac cycle of theheart based on detected timing of the target cardiac cycle.

In some embodiments, the controller controls output of the VAD based onan activity level of the patient. For example, in some embodiments, thecontroller: (a) processes the accelerometer output to measure anactivity level of the patient, and (b) controls the rotational speed ofthe impeller based on the activity level. In some embodiments, thecontroller: (a) processes the accelerometer output to measure arespiration rate for the patient and/or a diaphragm contraction for thepatient, and (b) bases the activity level on the respiration rate and/orthe diaphragm contraction. In some embodiments, the controller: (a)processes the accelerometer output to measure a contraction of theventricle, and (b) bases the activity level on the contraction of theventricle. In some embodiments, the controller: (a) processes theaccelerometer output to measure a heart rate of the patient, and (b)bases the activity level on the heart rate. In some embodiments, thecontroller: (a) processes the accelerometer output to detect anorientation of the patient, and (b) bases the activity level on theorientation of the patient. The activity level of the patient, on whichbasis the controller controls the rotational speed of the impeller, canbe defined to be any suitable function of one or more of the respirationrate of the patient, the diaphragm contraction for the patient, thecontraction of the ventricle, the heart rate of the patient, and theorientation of the patient.

The controller can be disposed in any suitable location. For example, insome embodiments, the controller is disposed within a housing of theVAD. In some embodiments, the blood circulation assist system furtherincludes an external control unit operatively coupled with the VAD, andthe controller is disposed within a housing of the external controlunit.

Any suitable accelerometer can be employed. For example, in someembodiments, the accelerometer output is indicative of accelerations ofthe VAD relative to three different axes.

In another aspect, a blood circulation assist system includes aventricular assist device (VAD) and a controller. The VAD is coupleableto a heart of a patient to pump blood from a ventricle of the heart intoa blood vessel of the patient. The VAD includes an accelerometergenerating an accelerometer output indicative of accelerations of theVAD. The controller processes the accelerometer output to generatepatient monitoring data for the patient indicative of one or morephysiological parameters of the patient.

The patient monitoring data can include any suitable data that can begenerated by processing the accelerometer output. For example, in someembodiments, the patient monitoring data includes orientations of thepatient and/or the VAD. In some embodiments, the patient monitoring dataincludes activity levels of the patient. In some embodiments, thepatient monitoring data includes respiration rates and/or diaphragmcontraction amplitudes. In some embodiments, the patient monitoring dataincludes contraction amplitudes for the ventricle. In some embodiments,the patient monitoring data includes heart rates of the patient. In someembodiments, the patient monitoring data is indicative of whether ablood clot has passed through the VAD during an acquisition time periodfor the patient monitoring data. In some embodiments, the patientmonitoring data is indicative of whether the patient suffers from aorticinsufficiency. In some embodiments, the patient monitoring data isindicative of whether arrhythmia has occurred during an acquisition timeperiod for the patient monitoring data. In some embodiments, the patientmonitoring data is indicative of whether the VAD has migrated/shiftedposition and/or the heart has remodeled.

In many embodiments, the blood circulation assist system includes amemory device in which the patient monitoring data is stored. In suchembodiments, the patient monitoring data stored in the memory device isaccessible for subsequent display and/or processing.

In another aspect, a blood circulation assist system includes aventricular assist device (VAD) and a controller. The VAD is coupleableto a heart of a patient to pump blood from a ventricle of the heart intoa blood vessel of the patient. The VAD includes an accelerometergenerating an accelerometer output indicative of accelerations of theVAD. The controller processes the accelerometer output to generate VADmonitoring data indicative of one or more operational parameters of theVAD.

The VAD monitoring data can include any suitable data that can begenerated by processing the accelerometer output. For example, in someembodiments: (a) the VAD includes an impeller and a motor statoroperable to rotate the impeller, and (b) the VAD monitoring data isindicative of vibrations of the impeller. In some embodiments, the VADmonitoring data is indicative of whether a suction event has occurredduring an acquisition time period for the VAD monitoring data.

In many embodiments, the blood circulation assist system includes amemory device in which the VAD monitoring data is stored. In suchembodiments, the VAD monitoring data stored in the memory device isaccessible for subsequent display and/or processing.

For a fuller understanding of the nature and advantages of the presentinvention, reference should be made to the ensuing detailed descriptionand accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a mechanical circulatory support systemthat includes a ventricular assist device (VAD) implanted in a patient'sbody, in accordance with many embodiments.

FIG. 2 is an exploded view of implanted components of the circulatorysupport system of FIG. 1.

FIG. 3 is an illustration of the VAD of FIG. 1 attached to the patient'sheart to augment blood pumping by the patient's left ventricle.

FIG. 4 is a cross-sectional view of the VAD of FIG. 3.

FIG. 5 is an illustration of an embodiment of a control unit for the VADof FIG. 3.

FIG. 6 is a heart-side view of the control unit of FIG. 5 showing athree-axis accelerometer included in the control unit, in accordancewith many embodiments.

FIG. 7 is a schematic diagram of a control system architecture of themechanical support system of FIG. 1.

FIG. 8 is a plot of raw accelerations of the VAD generated via thethree-axis accelerometer of FIG. 6.

FIG. 9 is a plot of mean normalized accelerations of the VAD generatedfrom the raw accelerations of FIG. 8.

FIG. 10 is a plot of velocities of the VAD generated from theaccelerations of FIG. 8.

FIG. 11 is a plot of displacements of the VAD generated from thevelocities of FIG. 10.

FIG. 12 illustrates synchronization of speed variation of the VAD ofFIG. 3 with ventricular systole based on heart sounds, ventricular wallmotion, and/or pump operating parameters, in accordance with manyembodiments.

FIG. 13 is a simplified schematic diagram of a method of operating theVAD of FIG. 1 utilizing accelerations measured via the accelerometer ofFIG. 6, in accordance with many embodiments.

DETAILED DESCRIPTION

In the following description, various embodiments of the presentinvention will be described. For purposes of explanation, specificconfigurations and details are set forth in order to provide a thoroughunderstanding of the embodiments. However, it will also be apparent toone skilled in the art that the present invention may be practicedwithout the specific details. Furthermore, well-known features may beomitted or simplified in order not to obscure the embodiment beingdescribed.

Referring now to the drawings, in which like reference numeralsrepresent like parts throughout the several views, FIG. 1 is anillustration of a mechanical circulatory support system 10 that includesa ventricular assist device (VAD) 14 implanted in a patient's body 12.The mechanical circulatory support system 10 includes the VAD 14, aventricular cuff 16, an outflow cannula 18, an external systemcontroller 20, and power sources 22. A VAD 14 can be attached to an apexof the left ventricle, as illustrated, or the right ventricle, or aseparate VAD can be attached to each of the ventricles of the heart 24.The VAD 14 can be capable of pumping the entire flow of blood deliveredto the left ventricle from the pulmonary circulation (i.e., up to 10liters per minute). Related blood pumps applicable to the presentinvention are described in greater detail below and in U.S. Pat. Nos.5,695,471, 6,071,093, 6,116,862, 6,186,665, 6,234,772, 6,264,635,6,688,861, 7,699,586, 7,976,271, 7,997,854, 8,007,254, 8,152,493,8,419,609, 8,652,024, 8,668,473, 8,852,072, 8,864,643, 8,882,744,9,068,572, 9,091,271, 9,265,870, and 9,382,908, all of which areincorporated herein by reference for all purposes in their entirety.With reference to FIG. 1 and FIG. 2, the VAD 14 can be attached to theheart 24 via the ventricular cuff 16, which can be sewn to the heart 24and coupled to the VAD 14. In the illustrated embodiment, the output ofthe VAD 14 connects to the ascending aorta via the outflow cannula 18 sothat the VAD 14 effectively diverts blood from the left ventricle andpropels it to the aorta for circulation through the rest of thepatient's vascular system.

FIG. 1 illustrates the mechanical circulatory support system 10 duringbattery 22 powered operation. A driveline 26 that exits through thepatient's abdomen 28 connects the VAD 14 to the external systemcontroller 20, which monitors system 10 operation. Related controllersystems applicable to the present invention are described in greaterdetail below and in U.S. Pat. Nos. 5,888,242, 6,991,595, 8,323,174,8,449,444, 8,506,471, 8,597,350, and 8,657,733, EP 1812094, and U.S.Patent Publication Nos. 2005/0071001 and 2013/0314047, all of which areincorporated herein by reference for all purposes in their entirety. Thesystem 10 can be powered by either one, two, or more batteries 22. Itwill be appreciated that although the system controller 20 and powersource 22 are illustrated outside/external to the patient body 12, thedriveline 26, the system controller 20 and/or the power source 22 can bepartially or fully implantable within the patient 12, as separatecomponents or integrated with the VAD 14. Examples of such modificationsare further described in U.S. Pat. Nos. 8,562,508 and 9,079,043, all ofwhich are incorporated herein by reference for all purposes in theirentirety.

With reference to FIG. 3 and FIG. 4, the VAD 14 has a circular shapedhousing 110 and is shown implanted within the patient 12 with a firstface 111 of the housing 110 positioned against the patient's heart 24and a second face 113 of the housing 110 facing away from the heart 24.The first face 111 of the housing 110 includes an inlet cannula 112extending into the left ventricle LV of the heart 24. The second face113 of the housing 110 has a chamfered edge 114 to avoid irritatingother tissue that may come into contact with the VAD 14, such as thepatient's diaphragm. To construct the illustrated shape of thepuck-shaped housing 110 in a compact form, a stator 120 and electronics130 of the VAD 14 are positioned on the inflow side of the housingtoward first face 111, and a rotor 140 of the VAD 14 is positioned alongthe second face 113. This positioning of the stator 120, electronics130, and rotor 140 permits the edge 114 to be chamfered along thecontour of the rotor 140, as illustrated in at least FIG. 3 and FIG. 4,for example.

Referring to FIG. 4, the VAD 14 includes a dividing wall 115 within thehousing 110 defining a blood flow conduit 103. The blood flow conduit103 extends from an inlet opening 101 of the inlet cannula 112 throughthe stator 120 to an outlet opening 105 defined by the housing 110. Therotor 140 is positioned within the blood flow conduit 103. The stator120 is disposed circumferentially about a first portion 140 a of therotor 140, for example about a permanent magnet 141. The stator 120 isalso positioned relative to the rotor 140 such that, in use, blood flowswithin the blood flow conduit 103 through the stator 120 before reachingthe rotor 140. The permanent magnet 141 has a permanent magnetic northpole N and a permanent magnetic south pole S for combined active andpassive magnetic levitation of the rotor 140 and for rotation of therotor 140. The rotor 140 also has a second portion 140 b that includesimpeller blades 143. The impeller blades 143 are located within a volute107 of the blood flow conduit such that the impeller blades 143 arelocated proximate to the second face 113 of the housing 110.

The puck-shaped housing 110 further includes a peripheral wall 116 thatextends between the first face 111 and a removable cap 118. Asillustrated, the peripheral wall 116 is formed as a hollow circularcylinder having a width W between opposing portions of the peripheralwall 116. The housing 110 also has a thickness T between the first face111 and the second face 113 that is less than the width W. The thicknessT is from about 0.5 inches to about 1.5 inches, and the width W is fromabout 1 inch to about 4 inches. For example, the width W can beapproximately 2 inches, and the thickness T can be approximately 1 inch.

The peripheral wall 116 encloses an internal compartment 117 thatsurrounds the dividing wall 115 and the blood flow conduit 103, with thestator 120 and the electronics 130 disposed in the internal compartment117 about the dividing wall 115. The removable cap 118 includes thesecond face 113, the chamfered edge 114, and defines the outlet opening105. The cap 118 can be threadedly engaged with the peripheral wall 116to seal the cap 118 in engagement with the peripheral wall 116. The cap118 includes an inner surface 118 a of the cap 118 that defines thevolute 107 that is in fluid communication with the outlet opening 105.

Within the internal compartment 117, the electronics 130 are positionedadjacent to the first face 111 and the stator 120 is positioned adjacentto the electronics 130 on an opposite side of the electronics 130 fromthe first face 111. The electronics 130 include circuit boards 131 andvarious components carried on the circuit boards 131 to control theoperation of the VAD 14 (e.g., magnetic levitation and/or drive of therotor) by controlling the electrical supply to the stator 120. Thehousing 110 is configured to receive the circuit boards 131 within theinternal compartment 117 generally parallel to the first face 111 forefficient use of the space within the internal compartment 117. Thecircuit boards also extend radially-inward towards the dividing wall 115and radially-outward towards the peripheral wall 116. For example, theinternal compartment 117 is generally sized no larger than necessary toaccommodate the circuit boards 131, and space for heat dissipation,material expansion, potting materials, and/or other elements used ininstalling the circuit boards 131. Thus, the external shape of thehousing 110 proximate the first face 111 generally fits the shape of thecircuits boards 131 closely to provide external dimensions that are notmuch greater than the dimensions of the circuit boards 131.

With continued reference to FIG. 4, the stator 120 includes a back iron121 and pole pieces 123 a-123 f arranged at intervals around thedividing wall 115. The back iron 121 extends around the dividing wall115 and is formed as a generally flat disc of a ferromagnetic material,such as steel, in order to conduct magnetic flux. The back iron 121 isarranged beside the control electronics 130 and provides a base for thepole pieces 123 a-123 f.

Each of the pole piece 123 a-123 f is L-shaped and has a drive coil 125for generating an electromagnetic field to rotate the rotor 140. Forexample, the pole piece 123 a has a first leg 124 a that contacts theback iron 121 and extends from the back iron 121 towards the second face113. The pole piece 123 a can also have a second leg 124 b that extendsfrom the first leg 124 a through an opening of a circuit board 131towards the dividing wall 115 proximate the location of the permanentmagnet 141 of the rotor 140. In an aspect, each of the second legs 124 bof the pole pieces 123 a-123 f is sticking through an opening of thecircuit board 131. In an aspect, each of the first legs 124 a of thepole pieces 123 a-123 f is sticking through an opening of the circuitboard 131. In an aspect, the openings of the circuit board are enclosingthe first legs 124 a of the pole pieces 123 a-123 f.

In a general aspect, the VAD 14 can include one or more Hall sensorsthat may provide an output voltage, which is directly proportional to astrength of a magnetic field that is located in between at least one ofthe pole pieces 123 a-123 f and the permanent magnet 141, and the outputvoltage may provide feedback to the control electronics 130 of the VAD14 to determine if the rotor 140 and/or the permanent magnet 141 is notat its intended position for the operation of the VAD 14. For example, aposition of the rotor 140 and/or the permanent magnet 141 can beadjusted, e.g., the rotor 140 or the permanent magnet 141 may be pushedor pulled towards a center of the blood flow conduit 103 or towards acenter of the stator 120.

Each of the pole pieces 123 a-123 f also has a levitation coil 127 forgenerating an electromagnetic field to control the radial position ofthe rotor 140. Each of the drive coils 125 and the levitation coils 127includes multiple windings of a conductor around the pole pieces 123a-123 f. Particularly, each of the drive coils 125 is wound around twoadjacent ones of the pole pieces 123, such as pole pieces 123 d and 123e, and each levitation coil 127 is wound around a single pole piece. Thedrive coils 125 and the levitation coils 127 are wound around the firstlegs of the pole pieces 123, and magnetic flux generated by passingelectrical current though the coils 125 and 127 during use is conductedthrough the first legs and the second legs of the pole pieces 123 andthe back iron 121. The drive coils 125 and the levitation coils 127 ofthe stator 120 are arranged in opposing pairs and are controlled todrive the rotor and to radially levitate the rotor 140 by generatingelectromagnetic fields that interact with the permanent magnetic poles Sand N of the permanent magnet 141. Because the stator 120 includes boththe drive coils 125 and the levitation coils 127, only a single statoris needed to levitate the rotor 140 using only passive and activemagnetic forces. The permanent magnet 141 in this configuration has onlyone magnetic moment and is formed from a monolithic permanent magneticbody 141. For example, the stator 120 can be controlled as discussed inU.S. Pat. No. 6,351,048, the entire contents of which are incorporatedherein by reference for all purposes. The control electronics 130 andthe stator 120 receive electrical power from a remote power supply via acable 119 (FIG. 3). Further related patents, namely U.S. Pat. Nos.5,708,346, 6,053,705, 6,100,618, 6,222,290, 6,249,067, 6,278,251,6,351,048, 6,355,998, 6,634,224, 6,879,074, and 7,112,903, all of whichare incorporated herein by reference for all purposes in their entirety.

The rotor 140 is arranged within the housing 110 such that its permanentmagnet 141 is located upstream of impeller blades in a location closerto the inlet opening 101. The permanent magnet 141 is received withinthe blood flow conduit 103 proximate the second legs 124 b of the polepieces 123 to provide the passive axial centering force thoughinteraction of the permanent magnet 141 and ferromagnetic material ofthe pole pieces 123. The permanent magnet 141 of the rotor 140 and thedividing wall 115 form a gap 108 between the permanent magnet 141 andthe dividing wall 115 when the rotor 140 is centered within the dividingwall 115. The gap 108 may be from about 0.2 millimeters to about 2millimeters. For example, the gap 108 can be approximately 1 millimeter.The north permanent magnetic pole N and the south permanent magneticpole S of the permanent magnet 141 provide a permanent magneticattractive force between the rotor 140 and the stator 120 that acts as apassive axial centering force that tends to maintain the rotor 140generally centered within the stator 120 and tends to resist the rotor140 from moving towards the first face 111 or towards the second face113. When the gap 108 is smaller, the magnetic attractive force betweenthe permanent magnet 141 and the stator 120 is greater, and the gap 108is sized to allow the permanent magnet 141 to provide the passivemagnetic axial centering force having a magnitude that is adequate tolimit the rotor 140 from contacting the dividing wall 115 or the innersurface 118 a of the cap 118. The rotor 140 also includes a shroud 145that covers the ends of the impeller blades 143 facing the second face113 that assists in directing blood flow into the volute 107. The shroud145 and the inner surface 118 a of the cap 118 form a gap 109 betweenthe shroud 145 and the inner surface 118 a when the rotor 140 islevitated by the stator 120. The gap 109 is from about 0.2 millimetersto about 2 millimeters. For example, the gap 109 is approximately 1millimeter.

As blood flows through the blood flow conduit 103, blood flows through acentral aperture 141 a formed through the permanent magnet 141. Bloodalso flows through the gap 108 between the rotor 140 and the dividingwall 115 and through the gap 109 between the shroud 145 and the innersurface 108 a of the cap 118. The gaps 108 and 109 are large enough toallow adequate blood flow to limit clot formation that may occur if theblood is allowed to become stagnant. The gaps 108 and 109 are also largeenough to limit pressure forces on the blood cells such that the bloodis not damaged when flowing through the VAD 14. As a result of the sizeof the gaps 108 and 109 limiting pressure forces on the blood cells, thegaps 108 and 109 are too large to provide a meaningful hydrodynamicsuspension effect. That is to say, the blood does not act as a bearingwithin the gaps 108 and 109, and the rotor is onlymagnetically-levitated. In various embodiments, the gaps 108 and 109 aresized and dimensioned so the blood flowing through the gaps forms a filmthat provides a hydrodynamic suspension effect. In this manner, therotor can be suspended by magnetic forces, hydrodynamic forces, or both.

Because the rotor 140 is radially suspended by active control of thelevitation coils 127 as discussed above, and because the rotor 140 isaxially suspended by passive interaction of the permanent magnet 141 andthe stator 120, no magnetic-field generating rotor levitation componentsare needed proximate the second face 113. The incorporation of all thecomponents for rotor levitation in the stator 120 (i.e., the levitationcoils 127 and the pole pieces 123) allows the cap 118 to be contoured tothe shape of the impeller blades 143 and the volute 107. Additionally,incorporation of all the rotor levitation components in the stator 120eliminates the need for electrical connectors extending from thecompartment 117 to the cap 118, which allows the cap to be easilyinstalled and/or removed and eliminates potential sources of pumpfailure.

In use, the drive coils 125 of the stator 120 generates electromagneticfields through the pole pieces 123 that selectively attract and repelthe magnetic north pole N and the magnetic south pole S of the rotor 140to cause the rotor 140 to rotate within stator 120. For example, the oneor more Hall sensors may sense a current position of the rotor 140and/or the permanent magnet 141, wherein the output voltage of the oneor more Hall sensors may be used to selectively attract and repel themagnetic north pole N and the magnetic south pole S of the rotor 140 tocause the rotor 140 to rotate within stator 120. As the rotor 140rotates, the impeller blades 143 force blood into the volute 107 suchthat blood is forced out of the outlet opening 105. Additionally, therotor draws blood into VAD 14 through the inlet opening 101. As blood isdrawn into the blood pump by rotation of the impeller blades 143 of therotor 140, the blood flows through the inlet opening 101 and flowsthrough the control electronics 130 and the stator 120 toward the rotor140. Blood flows through the aperture 141 a of the permanent magnet 141and between the impeller blades 143, the shroud 145, and the permanentmagnet 141, and into the volute 107. Blood also flows around the rotor140, through the gap 108 and through the gap 109 between the shroud 145and the inner surface 118 a of the cap 118. The blood exits the volute107 through the outlet opening 105, which may be coupled to an outflowcannula.

FIG. 5 shows a Hall Sensor assembly 200 for the VAD 14, in accordancewith many embodiments. The Hall Sensor assembly 200 includes a printedcircuit board (PCB) 202 and six individual Hall Effect sensors 208supported by the printed circuit board 202. The Hall Effect sensors 208are configured to transduce a position of the rotor 140 of the VAD 14.In the illustrated embodiment, the Hall Effect sensors 208 are supportedso as to be standing orthogonally relative to the PCB 202 and a longestedge of each of the Hall Effect sensors 208 is aligned to possess anorthogonal component with respect to the surface of the PCB 202. Each ofthe Hall Effect sensors 208 generates an output voltage, which isdirectly proportional to a strength of a magnetic field that is locatedin between at least one of the pole pieces 123 a-123 f and the permanentmagnet 141. The voltage output by each of the Hall Effect sensors 208 isreceived by the control electronics 130, which processes the sensoroutput voltages to determine the position and orientation of the rotor140. The determined position and orientation of the rotor 140 is used todetermine if the rotor 140 is not at its intended position for theoperation of the VAD 14. For example, a position of the rotor 140 and/orthe permanent magnet 141 may be adjusted, for example, the rotor 140 orthe permanent magnet 141 may be pushed or pulled towards a center of theblood flow conduit 103 or towards a center of the stator 120. Thedetermined position of the rotor 140 can also be used to determine rotoreccentricity or a target rotor eccentricity, which can be used asdescribed in U.S. Pat. No. 9,901,666, all of which is incorporatedherein by reference for all purposes in its entirety, to estimate flowrate of blood pumped by the VAD 14.

FIG. 6 is a heart-side view of the control electronics 130 showing anaccelerometer 210 included in the control electronics 130, in accordancewith many embodiments. In the many embodiments, the accelerometer 210 isa three-axis accelerometer that measures accelerations experienced bythe control electronics 130 (and thereby the VAD 14) in three orthogonalaxes (i.e., an X-axis 212, a Y-axis 214, and a Z-axis 216). In theillustrated embodiment, the X-axis 212 and the Y-axis 214 are eachoriented orthogonal to an axis of rotation of the rotor 140, and theZ-axis 216 is parallel to the axis of rotation of the rotor 140.

FIG. 7 is a schematic diagram of a control system architecture of themechanical support system 10. The driveline 26 couples the implanted VAD14 to the external system controller 20, which monitors system operationvia various software applications.

The VAD 14 includes the control electronics 130, the Hall Effect Sensorassembly 200, the motor stator 120, the rotor/impeller 140. In theillustrated embodiment, the control electronics include a processor 218,a memory device 220 (which can include read-only memory and/or randomaccess-memory), the accelerometer 210, a motor control unit 222, and acommunication unit 224. In some embodiments, the memory device 220stores one or more software applications that are executable by theprocessor 218 for various functions. For example, the one or moresoftware applications can effectuate control the motor control unit 222to effectuate radial levitation and rotational drive of the rotor 140during operation. In some embodiments, the one or more programseffectuate processing of output from the accelerometer 210 and/oroperational parameters for the VAD 14 (e.g., drive current, rotationalspeed, flow rate, pressure differential across the impeller) asdescribed herein to detect and/or measure patient physiological eventsand/or activity (e.g., patient orientation, patient activity level,heart wall motion, heart sounds, heart rate, respiratory rate, diaphragmcontraction, cardiac cycle timing). The one or more programs caneffectuate control of the motor control unit 222 to synchronizevariation in output of the VAD 14 with the patient's cardiac cycletiming as described herein. For example, the output of the VAD 14 can beincreased over a period of time during ventricular systole so as toaugment pumping of blood that occurs via contraction of the ventricle,thereby reducing the associated load on the ventricle. The one or moreprograms can effectuate control of the motor control unit 222 to varyoutput of the VAD 14 based on patient activity level. For example, inmany embodiments, the output of the VAD 14 is increased in response toincreased patient activity and decreased in response to decreasedpatient activity. The one or more programs can also be used toeffectuate processing of the output from the accelerometer 210 and/orthe operational parameters for the VAD 14 to generate patient monitoringdata and/or VAD monitoring data as described herein. The communicationunit 224 provides for wired and/or wireless communication between theVAD 14 and the external system controller 20. In some embodiments, themotor control unit 222 is included in the VAD 14. In other embodiments,the motor control unit 222 is included in the external system controller20.

The external system controller 20 can in turn be coupled to thebatteries 22 or an AC power module 30 that connects to an AC electricaloutlet. The external system controller 20 can include a processor 226, amemory device 228 (which can include read-only memory and/or randomaccess-memory), an emergency backup battery (EBB) to power the system(e.g., when the batteries 22 are depleted), one or more display units230, one or more input/output devices 232, and a communication unit 234,which can have Bluetooth capabilities for wireless data communication.An external computer having a system monitor 32 (which can be operatedby a clinician or patient) may further be coupled to the circulatorysupport system 10 for configuring the external system controller 20, theimplanted VAD 14, and/or patient specific parameters; updating softwareon the external system controller 20 and/or the implanted VAD 14;monitoring system operation; and/or as a conduit for system inputs oroutputs.

In some embodiments, the memory device 228 stores one or more softwareapplications that are executable by the processor 226 for variousfunctions. For example, the one or more software applications caneffectuate control the motor control unit 222 to effectuate radiallevitation and rotational drive of the rotor 140 during operation. Insome embodiments, the one or more programs effectuate processing ofoutput from the accelerometer 210 and/or operational parameters for theVAD 14 (e.g., drive current, rotational speed, flow rate, pressuredifferential across the impeller) as described herein to detect and/ormeasure patient physiological events and/or activity (e.g., patientorientation, patient activity level, heart wall motion, heart sounds,heart rate, respiratory rate, diaphragm contraction, cardiac cycletiming). The one or more programs can effectuate control of the motorcontrol unit 222 to synchronize variation in output of the VAD 14 withthe patient's cardiac cycle timing as described herein. For example, theoutput of the VAD 14 can be increased over a period of time duringventricular systole so as to augment pumping of blood that occurs viacontraction of the ventricle, thereby reducing the associated load onthe ventricle. The one or more programs can effectuate control of themotor control unit 222 to vary output of the VAD 14 based on patientactivity level. For example, in many embodiments, the output of the VAD14 is increased in response to increased patient activity and decreasedin response to decreased patient activity. The one or more programs canalso be used to effectuate processing of the output from theaccelerometer 210 and/or the operational parameters for the VAD 14 togenerate patient monitoring data and/or VAD monitoring data as describedherein. The communication unit 234 provides for wired and/or wirelesscommunication between the external system controller 20 and the VAD 14and/or the system monitor 32.

VAD Accelerations

FIG. 8 is a plot of raw accelerations of the VAD 14 measured by thethree-axis accelerometer 210 during an animal study. The rawaccelerations shown include X-axis acceleration 236, Y-axis acceleration238, Z-axis acceleration 240, and a magnitude 242 of the rawacceleration. FIG. 8 also shows a flow rate 244 of the VAD 14 during themeasurement of the raw accelerations.

FIG. 9 is a plot of mean normalized accelerations of the VAD 14generated from the raw accelerations of FIG. 8. The mean normalizedaccelerations shown include X-axis mean normalized acceleration 246,Y-axis mean normalized acceleration 248, Z-axis mean normalizedacceleration 250, and a magnitude 252 of the mean normalizedacceleration. Each of the mean accelerations was produced by subtractingthe corresponding average acceleration over the entire sample periodfrom the corresponding raw acceleration plot (so that the resultingaverage is zero). FIG. 9 also shows the flow rate 244 of the VAD 14during the measurement of the raw accelerations. To enhance legibilityof FIG. 9, a constant acceleration offset has been combined with each ofthe acceleration components (i.e., 300 mg added to the X-axis meannormalized acceleration 246, 100 mg has been added to the Y-axis meannormalized acceleration 248, 100 mg has been subtracted from the Z-axismean normalized acceleration 250, and 300 mg has been subtracted fromthe magnitude 252 of the total mean normalized acceleration) so as toseparate the plotted components.

FIG. 10 is a plot of velocities of the VAD 14 generated via integrationof the mean normalized accelerations of FIG. 9. The output from at leastthree accelerometers (or one accelerometer and one gyroscope) can beintegrated to determine the corresponding three-dimensional velocity.With fewer accelerometers, significant amounts of rotational motion mayinduce significant levels of error in the resulting three-dimensionalvelocity. While one accelerometer can provide reasonable estimates ofthe velocity if the rotational motions are insignificant, rotationalmotions of a VAD may be significant. For example, if the beating of theheart rocks the accelerometer back and forth in a motion that includesrotation, an error due to centripetal acceleration may accumulate. Theerror may be quite small for a time, but may grow in size over time. Inmany embodiments, acceleration due to gravity is filtered out prior tointegrating the accelerations to determine the three-dimensionalvelocity. The velocities shown include X-axis velocity 254, Y-axisvelocity 256, Z-axis velocity 258, and total velocity 260. FIG. 10 alsoshows the flow rate 244 of the VAD 14 during the measurement of the rawaccelerations. To enhance legibility of FIG. 10, a constant velocityoffset has been combined with each of the velocity components (i.e., 30mm/sec added to the X-axis velocity 254, 10 mm/sec has been added to theY-axis velocity 256, 10 mm/sec has been subtracted from the Z-axisvelocity 258, and 30 mm/sec has been subtracted from the total velocity260) so as to separate the plotted components.

FIG. 11 is a plot of displacements of the VAD 14 generated viaintegration of the velocities of FIG. 10. The displacements showninclude X-axis displacement 262, Y-axis displacement 264, Z-axisdisplacement 266, and total displacement 268. FIG. 11 also shows theflow rate 244 of the VAD 14 during the measurement of the rawaccelerations. To enhance legibility of FIG. 11, a constant displacementoffset has been combined with each of the displacement components (i.e.,1 mm added to the X-axis displacement 262, 0.3 mm has been added to theY-axis displacement 264, 0.3 mm has been subtracted from the Z-axisdisplacement 266, and 30 mm/sec has been subtracted from the totaldisplacement 268) so as to separate the plotted components.

Pump/Patient Orientation

In many embodiments, the output from the accelerometer 210 includesacceleration due to gravity and is therefore indicative of theorientation of the VAD 14, and therefore also the patient 12, relativeto vertical. Any suitable approach can be used to process the outputfrom the accelerometer 210 to determine the orientation of the patient12 and/or the VAD 12 relative to vertical. For example, each of theX-axis acceleration 236, Y-axis acceleration 238, and Z-axisacceleration 240 can be processed to calculate a respective runningaverage having a suitable time period (e.g., 10 to 15 seconds)corresponding to an X-axis gravity induced acceleration, a Y-axisgravity induced acceleration, and a Z-axis gravity induced acceleration,respectively. The X-axis gravity induced acceleration, Y-axis gravityinduced acceleration, and the Z-axis gravity induced acceleration definea gravity vector that indicates the orientation of the accelerometerrelative to vertical. Any suitable approach can be used to process thegravity vector to generate an indication of the orientation of thepatient relative to a suitable reference axis or reference direction.For example, the gravity vector can be transformed from theaccelerometer axis system to a patient reference axis system, forexample, with a patient X-axis extending forward relative to thepatient's thorax, a patient Y-axis extending to the left relative to thepatient's thorax, and a patient Z-axis extending toward the top of thepatient's thorax. As another example, reference gravity orientationvectors corresponding to known orientations of the patient 12 and/or theVAD 14 can be generated by placing the patient 12 and/or the VAD 14 inknown orientations relative to vertical (e.g., standing upright, layinghorizontal on the patient's left side, laying horizontal on thepatient's right side, laying horizontal on the patient's back, andlaying horizontal on the patient's stomach). The gravity vector can becompared to each of one or more of the reference gravity orientationvectors using a known approach to determine a relative angle between thegravity vector and the respective reference gravity orientation vector.The resulting relative angle(s) are indicative of the orientation of thepatient 12 and/or the VAD 14 relative to the reference orientations ofthe patient 12 and/or the VAD 14.

Lung/Diaphragm Motion

The patient's respiration rate and the diaphragm contraction amplitudecan be determined by processing the accelerometer output using asuitable band-pass filter (e.g., approximately 0.2 to 1.0 Hz (12 to 60breaths per minute)) to isolate accelerations due to respiration. Theresulting accelerations due to respiration can then be processed todetermine corresponding respiration rate and diaphragm contractionamplitude. Frequency range and direction of movement can be used toisolate respiratory motion. In addition, accelerations due torespiration will typically have lower amplitudes (1 to 10 mg) and aregular pattern.

Heart Wall Motion

In some embodiments, the motion of the ventricular heart wall ismonitored by processing the accelerometer output using a suitableband-pass filter (e.g., primary left ventrical wall motion range shouldbe 0.5 to 3 Hz (30 to 180 BPM)) to isolate accelerations due to theventricular heart wall motion. The heart wall motion can be processed todetermine cardiac cycle timing, ventricle contractile strength, andventricle contractile efficiency. Direction (z-axis, in line with theinflow cannula), frequency range, and timing regularity can be used toisolate LV wall motion. Transitions from periods of low accelerations tohigh accelerations (or changes in acceleration, jerk) can be used toindicate the start of a cardiac cycle (start of systole). Maximumacceleration can be used to estimate contractile strength. Contractilestrength combined with min/mean/max flow through the pump can then beused to estimate contractile efficiency. The ventricle contractilestrength and ventricle contractile efficiency can be monitored tomonitor health of the patient's heart (e.g., detect signs of recovery orweakening). The heart wall motion can also be monitored to detectarrhythmia. Irregular cardiac cycle timing periods (start of systole)can be used to detect arrhythmia. In addition, heart rates above andbelow a normal range can be used to detect arrhythmia.

Heart Sounds

In some embodiments, the accelerometer output is processed to detectand/or measure heart sounds. The heart sounds that can be detectedand/or measured include a first sound (S₁) generated by closing of theatrioventricular valves during ventricular contraction and a secondsound (S₂) generated by closing of the semilunar valves duringventricular diastole. In some patients, the occurrence of aorticinsufficiency (aka aortic regurgitation) generates a corresponding soundthat can be detected via the accelerometer 210. In some embodiments, theaccelerometer output is processed using a suitable band-pass filter(e.g., 50 to 500 Hz) to isolate accelerations due to the heart sounds.The accelerations due to the heart sounds can then be processed todetect/measure the heart sounds. The heart sounds can be used to monitorthe cardiac cycle timing of the heart, as well as to monitor the patientfor the occurrence of aortic insufficiency.

Pump Monitoring

In some embodiments, the accelerations measured by the accelerometer 210include accelerations induced via operation of the VAD 14. The inducedaccelerations can include accelerations induced via vibrations of therotor 140, speed of the rotor 140, change in speed of the rotor 140,and/or mass/balance of the rotor 140. Accelerations can also be inducedas the result of ingestion of an object, by the VAD 14 such as a bloodclot. Accelerations can also be induced by a suction event, which canoccur when the VAD 14 over-extracts blood from the ventricle. In someembodiments, the accelerometer output is processed using a suitableband-pass filter (e.g., 0.5 to 3.0 Hz) to isolate accelerations inducedvia operation of the VAD 14. The accelerations induced via operation ofthe VAD 14 can be processed to monitor for excessive rotor vibration,ingestion of an object, and/or the occurrence of a suction event. Forexample, a suitable band-pass filter can be applied around the operatingrotor speed (50-150 Hz) and potentially the subsequent harmonics.Changes in vibration amplitude (specifically increases) of the resultingfiltered accelerations can be indicative of a rotor imbalance caused byeither an ingested thrombus or thrombus forming on the rotor. Suctionevents can be detected via the combined occurrence of three events: (1)changes in LV wall motion (accelerometer), (2) low average flow throughthe pump (which can be detected via rotor drive current), and (3) lowminimal flow fluctuations (which can be detected via the occurrence ofsmall changes in drive current).

In some embodiments, the cardiac cycle timing of the patient is detectedvia monitoring of drive current supplied to the VAD 14, rotational speedof the rotor 140, flow rate of blood through the VAD 14, and/or pressuredifferential across the rotor 140. For example, during ventricularsystole, variation in the ventricular pressure induces correspondingchanges in the drive current supplied to the VAD 14 for a givenrotational speed of the rotor 140. In some embodiments, the rotationspeed of the rotor 140 is kept constant over one or more cardiac cyclesto avoid inducing changes in the drive current due to changes in therotational speed of the rotor 140. By monitoring the drive currentsupplied to the VAD 14, the cardiac cycle timing can be detected viadetection of the time periods corresponding to ventricular systole. Forexample, in many embodiments the rotor drive current essentially followsa sinusoidal shape throughout the cardiac cycle. Peak flows (and drivecurrent) occur at maximum left ventricle pressure, which is in themiddle of systole. Minimum flows (min drive current) occur at the lowestleft ventricle pressure, which is the start of diastole. In summary, thestart of diastole can be detected by detecting the minimum drivecurrent. Peak systole can be detected by detecting maximum drivecurrent. Start of systole can be detected by detecting a sudden changein drive current slope (dl/dt) at the end of diastole.

Pump Control Based on Patient Activity Level

In some embodiments, the output of the accelerometer 210 is processed tomeasure an activity level of the patient 12, including deducing thepatient's circadian rhythm. In some embodiments, the output of the VAD14 is varied based on the measured activity level so as to provideincreased support in response to an increase in the measured activitylevel and decreased support in response to a decrease in the activitylevel. In some embodiments, the average rotational speed of the rotor140 is increased to increase the output of the VAD 14 and the averagerotational speed is decreased to decrease the output of the VAD 14.

The output of the accelerometer 210 can be processed to measure a numberof different patient physiological processes that are indicative of theactivity level of the patient 12. For example, the accelerometer outputcan be processed using suitable approaches, such as those describedherein, to measure respiration rate, diaphragm contraction amplitude,ventricle contraction amplitude, heart rate, vibration fromwalking/running, and/or orientation of the patient 12. The activitylevel of the patient 12 can be defined to be a suitable function of oneor more of the respiration rate, the diaphragm contraction amplitude,the ventricle contraction amplitude, the heart rate, and/or theorientation of the patient 12.

Pump Synchronization with Patient Heart Cycle

In some embodiments, the output of the accelerometer 210 is processed todetect/measure the cardiac cycle timing for use in synchronization ofoperation of the VAD 14 with the cardiac cycle timing. The cardiac cycletiming can be determined based on any suitable indicator determined viaprocessing of the accelerometer output, such as heart wall motion andheart sounds. Additionally, the cardiac cycle timing can be determined,as described herein, based on pump operating parameters, such ascurrent, pump speed, and/or flow rate.

FIG. 12 illustrates synchronization of speed variation of the VAD 14with ventricular systole based on heart sounds, ventricular wall motion,and/or pump operating parameters, in accordance with many embodiments.At the beginning of the cardiac cycle, both the atria and ventricles arerelaxed (diastole). Blood flows into the atriums and into the ventriclesfrom the atriums. Contraction of the atria (atrial systole) pumpsadditional blood from the atriums into the ventricles. Atrial systoleends prior to ventricular systole. During ventricular systole, each ofthe ventricular pressures 270 (only one shown for clarity) increasesover the respective atrial pressure 272 (only one shown for clarity)thereby causing the respective atrial valve to close. The closing of theatrial valves generates the first heart sound (S₁). Further contractionof the respective ventricle increases the ventricular pressure 270 toabove the respective output blood vessel pressure (e.g., aortic pressure274), thereby causing the respective semilunar valve to open and bloodto flow out of the ventricle. Ventricular relaxation (ventriculardiastole) follows ventricular systole. As the ventricles relax, each ofthe ventricular pressures 270 drops below the respective output bloodvessel pressure, thereby causing the respective semilunar valve toclose. The closure of the semilunar valves generates the second heartsound (S₂). Further relaxation of the ventricles decreases each of theventricular pressures below the respective atrial pressure (e.g., leftatrial pressure 272), thereby causing the atrial valves to open.

Heart wall motion 276 during contraction of the ventricles duringventricular systole induces accelerations of the VAD 14 that aremeasured by the accelerometer 210. In the illustrated embodiment, theheart wall motion induced acceleration of the VAD 14 is primarilyreflected in the Z-axis acceleration 240 measured by the accelerometer210. Accordingly, the Z-axis displacement 266 can be processed tomonitor the heart wall motion 276 to measure timing and strength of eachventricular systole, and thereby indicating cardiac cycle timing.Detection of the heart sounds (S₁ and S₂) can also be used to determinethe cardiac cycle timing, either alone or in combination with the timingof ventricular systole determined via assessment of the heart wallmotion 276.

In some embodiments, the VAD 14 is operated so as to vary output of theVAD 14 in synchronization with the cardiac cycle timing. For example, insome embodiments, the VAD 14 is operated to pump blood at a greater rateduring ventricular systole than pumped by the VAD 14 during the rest ofthe cardiac cycle. In many embodiments, the rotation speed of the rotor140 is varied to vary the rate that blood is pumped by the VAD 14. Anysuitable variation of the output of the VAD 14 can be used. For example,as shown in FIG. 12, the rotational speed of the rotor 140 can be variedduring ventricular systole so as to increase the output of the VAD 14during ventricular systole. In the illustrated embodiment, therotational speed of the rotor 140 varied during ventricular systole(i.e., increased from a first rotational speed (r1) to a secondrotational speed (r2), maintained at the second rotational speed (r2)for a period of time, and then reduced back down to the first rotationalspeed (r1)).

Any suitable approach can be used to control timing of the variation inoutput of the VAD 14. For example, cardiac cycle timing observed duringone or more previous cardiac cycles can be used to control timing of thevariation in output of the VAD 14 during a current cardiac cycle. Asanother example, when sufficiently fast processing is utilized, cardiaccycle timing for a target cardiac cycle can be used to control timing ofthe variation in output of the VAD 14 during the target cardiac cycle.

Methods

FIG. 13 is a simplified schematic diagram of a method 300 in whichaccelerations of a VAD are measured and used to control operation of theVAD, monitor the patient in which the VAD is implanted, and/or monitoroperation of the VAD. Any suitable circulation assist system thatincludes a VAD, such as the circulation assist systems described herein,can be used to practice the method 300. Any suitable combination of thebelow described acts of the method 300 can be employed in any suitableorder. For example, any suitable set of the acts of the method 300 canbe employed to control operation of the VAD based on patient activitylevel. Any suitable set of the acts of the method 300 can be employed tocontrol operation of the VAD to vary output of the VAD in synch with apatient's cardiac cycle timing. Any suitable set of the acts of themethod 300 can be employed to monitor the patient. And any suitable setof the acts of the method 300 can be employed to monitor operation ofthe VAD.

In act 302, accelerations of the VAD are measured. Any suitable approachcan be used to measure the acceleration of the VAD. For example, in theVAD 14, the accelerations of the VAD 14 are measured via theaccelerometer 210.

In act 304, the measured accelerations of the VAD are processed tomonitor the orientation of the VAD and/or a patient in which the VAD isimplanted. For example, the measured accelerations can be processed asdescribed herein to monitor the orientation of the VAD and/or thepatient.

In act 306, the measured accelerations of the VAD are processed to trackthe patient's cardiac cycle timing. For example, the measuredaccelerations can be processed as described herein to track thepatient's cardiac cycle timing.

In act 308, operating parameters of the VAD are processed to track thepatient's cardiac cycle timing. For example, operating parameters of theVAD (e.g., drive current) can be processed as described herein to trackthe patient's cardiac cycle timing.

In act 310, the measured accelerations are processed to monitor thepatient's activity level. For example, the measured accelerations can beprocessed to monitor respiration rate, diaphragm contraction amplitude,heart rate, ventricle contraction amplitude, and/or the patient'sorientation to monitor the patient's activity level as described herein.

In act 312, operation of the VAD is controlled in synch with thepatient's cardiac cycle timing. For example, operation of the VAD 14 canbe controlled to increase output of the VAD 14 during ventricularsystole as described herein.

In act 314, operation of the VAD is controlled based on the patient'sactivity level. For example, the VAD 14 can be operated as describedherein to increase output of the VAD 14 in response to an increase inpatient activity level and to decrease output of the VAD 14 in responseto a decrease in patient activity level.

In act 316, the measured accelerations are processed to generate VADmonitoring data. For example, the measured accelerations of the VAD 14can be processed as described herein to generate VAD monitoring dataindicative of mass/balance of the rotor 140, detect ingestion of anobject (e.g., a blood clot) by the VAD 14, and/or detect a suctionevent.

In act 318, the measured accelerations are processed to generate patientmonitoring data. For example, the measured accelerations of the VAD 14can be processed as described herein to generate patient monitoring dataindicative of patient orientation, heart rate, respiration rate,ventricular contraction strength and/or efficiency, presence of absenceof arrhythmia, patient activity level, and/or presence or absence ofaortic insufficiency.

In act 320, the patient monitoring data is output for subsequentprocessing and/or display. For example, the patient monitoring data canbe stored in the VAD 14 and output to the system monitor 32 via theexternal system controller 20, or stored in the external systemcontroller 20 and output directly to the system monitor 32.

In act 322, the VAD monitoring data is output for subsequent processingand/or display. For example, the VAD monitoring data can be stored inthe VAD 14 and output to the system monitor 32 via the external systemcontroller 20, or stored in the external system controller 20 and outputdirectly to the system monitor 32.

Other variations are within the spirit of the present invention. Thus,while the invention is susceptible to various modifications andalternative constructions, certain illustrated embodiments thereof areshown in the drawings and have been described above in detail. It shouldbe understood, however, that there is no intention to limit theinvention to the specific form or forms disclosed, but on the contrary,the intention is to cover all modifications, alternative constructions,and equivalents falling within the spirit and scope of the invention, asdefined in the appended claims.

The use of the terms “a” and “an” and “the” and similar referents in thecontext of describing the invention (especially in the context of thefollowing claims) are to be construed to cover both the singular and theplural, unless otherwise indicated herein or clearly contradicted bycontext. The terms “comprising,” “having,” “including,” and “containing”are to be construed as open-ended terms (i.e., meaning “including, butnot limited to,”) unless otherwise noted. The term “connected” is to beconstrued as partly or wholly contained within, attached to, or joinedtogether, even if there is something intervening. Recitation of rangesof values herein are merely intended to serve as a shorthand method ofreferring individually to each separate value falling within the range,unless otherwise indicated herein, and each separate value isincorporated into the specification as if it were individually recitedherein. All methods described herein can be performed in any suitableorder unless otherwise indicated herein or otherwise clearlycontradicted by context. The use of any and all examples, or exemplarylanguage (e.g., “such as”) provided herein, is intended merely to betterilluminate embodiments of the invention and does not pose a limitationon the scope of the invention unless otherwise claimed. No language inthe specification should be construed as indicating any non-claimedelement as essential to the practice of the invention.

Preferred embodiments of this invention are described herein, includingthe best mode known to the inventors for carrying out the invention.Variations of those preferred embodiments may become apparent to thoseof ordinary skill in the art upon reading the foregoing description. Theinventors expect skilled artisans to employ such variations asappropriate, and the inventors intend for the invention to be practicedotherwise than as specifically described herein. Accordingly, thisinvention includes all modifications and equivalents of the subjectmatter recited in the claims appended hereto as permitted by applicablelaw. Moreover, any combination of the above-described elements in allpossible variations thereof is encompassed by the invention unlessotherwise indicated herein or otherwise clearly contradicted by context.

All references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

What is claimed is:
 1. A method of controlling operation of aventricular assist device (VAD) implanted within a patient, the methodcomprising: processing, by a controller, output of an accelerometer tomeasure accelerations of the VAD, wherein the VAD comprises theaccelerometer; processing, by the controller, the accelerations of theVAD to measure at least one of: an orientation of the patient, arespiratory activity of the patient, and a cardiac cycle timing of thepatient; controlling, by the controller, operation of the VAD based onat least one of the orientation of the patient, the respiratoryactivity, and the cardiac cycle timing.
 2. The method of claim 1,comprising: processing the accelerations of the VAD to determine theorientation of the patient; and controlling the operation of the VADbased on the orientation of the patient.
 3. The method of claim 2,wherein the orientation of the patient is measured relative to vertical.4. The method of claim 3, comprising comparing the orientation of thepatient to reference orientations of the patient to determine arespective relative angle between the orientation of the patient andeach of one or more reference orientations of the patient.
 5. The methodof claim 4, wherein the one or more reference orientations of thepatient comprise standing upright and laying horizontal.
 6. The methodof claim 4, wherein the one or more reference orientations of thepatient comprise standing upright, laying horizontal on the patient'sright side, laying horizontal on the patient's left side, layinghorizontal on the patient's stomach, and laying horizontal on thepatient's back.
 7. The method of claim 1, comprising: processing theaccelerations of the VAD to measure the respiratory activity; andcontrolling the operation of the VAD based on the respiratory activity.8. The method of claim 7, wherein the respiratory activity of thepatient comprises a respiration rate of the patient.
 9. The method ofclaim 8, wherein the respiratory activity of the patient comprises adiaphragm contraction amplitude of the patient.
 10. The method of claim1, comprising: processing the accelerations of the VAD to determine thecardiac cycle timing; and controlling the operation of the VAD based onthe cardiac cycle timing.
 11. The method of claim 10, comprising:processing the accelerations of the VAD to monitor a motion of aventricular heart wall of the patient; and processing the motion of theventricular heart wall to determine the cardiac cycle timing.
 12. Themethod of claim 10, comprising synchronizing a speed variation of theVAD with the cardiac cycle timing.
 13. The method of claim 10,comprising synchronizing a variation of a flow rate of blood pumped bythe VAD with the cardiac cycle timing.
 14. The method of claim 1,comprising: processing the accelerations of the VAD to monitor a motionof a ventricular heart wall of the patient; and processing the motion ofthe ventricular heart wall to determine ventricle contractile strengthand/or ventricle contractile efficiency to monitor health of thepatient's heart.
 15. The method of claim 1, comprising: processing theaccelerations of the VAD to monitor a motion of a ventricular heart wallof the patient; and processing the motion of the ventricular heart wallto monitor for an occurrence of arrhythmia.
 16. The method of claim 1,comprising monitoring the cardiac cycle timing for an occurrence ofarrhythmia.
 17. The method of claim 1, comprising: processing theaccelerations of the VAD to detect and/or measure heart sounds of thepatient; and processing the heart sounds to determine the cardiac cycletiming.
 18. The method of claim 1, comprising: processing theaccelerations of the VAD to detect and/or measure heart sounds of thepatient; and processing the heart sounds to monitor for an occurrence ofaortic insufficiency.
 19. The method of claim 1, wherein the processingof the accelerations of the VAD comprises isolating accelerationsinduced via operation of the VAD.
 20. The method of claim 19, comprisingprocessing the accelerations induced via operation of the VAD to monitorfor one or more of excessive vibration of a rotor of the VAD, ingestionof an object by the VAD, and an occurrence of a suction event.